1. Field of the Invention
The present invention relates to multilayer ceramic capacitors, in particular a multilayer ceramic capacitor that includes multilayer outer electrodes.
2. Description of the Related Art
Multilayer ceramic chip capacitors have been widely used in recent years. A multilayer ceramic capacitor includes a multilayer body and outer electrodes on the end surfaces of the multilayer body. The multilayer body is composed of alternately stacked ceramic layers and substantially flat-plate inner electrodes, and the outer electrodes are electrically coupled to the inner electrodes. In some multilayer ceramic capacitors, the outer electrodes have a multilayer structure for purposes such as improved mechanical strength. Japanese Unexamined Patent Application Publication No. 2014-116340 discloses a multilayer ceramic capacitor of this type.
This multilayer ceramic capacitor has five-layer outer electrodes. Each outer electrode has an underlying electrode layer in close contact with a multilayer body, a first intermediate metal layer in close contact with the surface of the underlying metal layer, an intermediate conductive resin layer in close contact with the surface of the first intermediate metal layer, a second intermediate metal layer in close contact with the surface of the intermediate conductive resin layer, and a surface metal layer in close contact with the surface of the second intermediate metal layer.
The underlying metal layer is made of a mixture of nickel, copper, palladium, platinum, silver, gold, or an alloy thereof and the base component of dielectric layers and a margin section or a mixture of such a metal or alloy and a glass component such as silica. The first and second intermediate metal layers are made of nickel, copper, palladium, platinum, silver, gold, or an alloy thereof. The surface metal layer is made of tin, palladium, gold, zinc, or an alloy thereof. The intermediate conductive resin layer is made of an epoxy resin that contains conductive filler. The conductive filler is a metal filler made of silver, copper, nickel, or an alloy thereof or a carbon filler.
The multilayer ceramic capacitor disclosed in Japanese Unexamined Patent Application Publication No. 2014-116340 has an intermediate conductive resin layer in the outer electrodes for improved mechanical strength. Formed to cover the surface of the first intermediate metal layer, the intermediate conductive resin layer does not firmly adhere to the first intermediate metal layer. Water and other contaminants easily penetrate into the space between the intermediate conductive resin layer and the first intermediate metal layer, and this affects the waterproof reliability and electrical characteristics of the multilayer ceramic capacitor. Furthermore, the electrical connections between the outer electrodes and the inner electrodes are not sufficiently reliable.